It is well known to identify objects with tags that can be monitored, sensed or interrogated from a remote location.
There are several types of RF-interrogated identification tags currently on the market. One example is the SMART Pass system developed by AMTECH Corp. of Dallas, Tex. Their system uses passive RF tags, a little larger than a standard credit card and nearly 1/2 an inch thick. The tags require a large, high-frequency antenna capable of sending a microwave-frequency RF pulse strong enough to energize the tag to the point where it can return its identification number. The maximum range of the AMTECH system is a few meters. The AMTECH system antenna is designed to be mounted on a metal pole. Its size (38.1 cm.times.41.7 cm.times.10.2 cm) and power requirements, are prohibitive for use in an office or hospital environment for tracking capital assets. The system does not allow tracking several objects simultaneously.
Other identification tag systems, such as Texas Instrument's TIRIS system, the Dutch NEDAP monitoring system, and the Israeli On-Track Innovations PorTrac system, are all distance limited solutions for remote, contactless, control of tags and objects. The practical reliable communication distance between tag and object is about 10 cm. Larger distances require very strong magnetic fields, utilizing large and costly hardware associated with them.
Currently available active or passive electronic tagging systems either require a large and costly portable monitoring antenna with limited interrogation range (several score centimeters), or a physical connection to the electronic tag.